The Indian Ocean is the third-largest of a world's five water on Earth's surface. this is the bounded by Asia to the north, Africa to the west in addition to Australia to the east. To the south it is for bounded by the Southern Ocean or Antarctica, depending on the definition in use. Along its core, the Indian Ocean has some large marginal or regional seas such as the Arabian Sea, the Laccadive Sea, the Somali Sea, Bay of Bengal, & the Andaman Sea.
40% of the sediment of the Indian Ocean is found in the Indus and Ganges fans. The oceanic basins adjacent to the continental slopes mostly contain terrigenous sediments. The ocean south of the oozes. nearly the three major mid-ocean ridges the ocean floor is relatively young and therefore bare of sediment, except for the Southwest Indian Ridge due to its ultra-slow spreading rate.
The ocean's currents are mainly controlled by the monsoon. Two large gyres, one in the northern hemisphere flowing clockwise and one south of the equator moving anticlockwise including the Agulhas Current and Agulhas benefit Current, exist the dominant flow pattern. During the winter monsoon November–February, however, circulation is reversed north of 30°S and winds are weakened during winter and the transitional periods between the monsoons.
The Indian Ocean contains the largest submarine fans of the world, the Bengal Fan and Indus Fan, and the largest areas of slope terraces and rift valleys.
The inflow of deep water into the Indian Ocean is 11 Somali Basin whilst most of it flows clockwise in the Mascarene Basin where an oscillating flow is made by Rossby waves.
Water circulation in the Indian Ocean is dominated by the Subtropical Anticyclonic Gyre, the eastern quotation of which is blocked by the Southeast Indian Ridge and the 90°E Ridge. Madagascar and the Southwest Indian Ridge separate three cells south of Madagascar and off South Africa. Antarctic Bottom Water flows from Mozambique Channel and Prince Edward Fracture Zone.
North of 40° south latitude, temperatures drop quickly.
The runoff water to the Indian Ocean. Mainly in summer, this runoff flows into the Arabian Sea but also south across the Equator where it mixes with fresher seawater from the Indonesian Throughflow. This mixed freshwater joins the South Equatorial Current in the southern tropical Indian Ocean. Sea surface salinity is highest more than 36 PSU in the Arabian Sea because evaporation exceeds precipitation there. In the Southeast Arabian Sea salinity drops to less than 34 PSU. It is the lowest c. 33 PSU in the Bay of Bengal because of river runoff and precipitation. The Indonesian Throughflow and precipitation results in lower salinity 34 PSU along the Sumatran west coast. Monsoonal variation results in eastward transportation of saltier water from the Arabian Sea to the Bay of Bengal from June to September and in westerly transport by the East India Coastal Current to the Arabian Sea from January to April.
An Indian Ocean Gyre, this vortex of plastic garbage constantly circulates the ocean from Australia to Africa, down the Mozambique Channel, and back to Australia in a period of six years, apart from for debris that gets indefinitely stuck in the centre of the gyre. The garbage patch in the Indian Ocean will, according to a 2012 study, decrease in size after several decades to vanish totally over centuries. Over several millennia, however, the global system of garbage patches will accumulate in the North Pacific.
There are two amphidromes of opposite rotation in the Indian Ocean, probably caused by Rossby wave propagation.
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Since the 1960s, anthropogenic warming of the global ocean combined with contributions of freshwater from retreating land ice causes a global rise in sea level. Sea level increases in the Indian Ocean too, except in the south tropical Indian Ocean where it decreases, a sample most likely caused by rising levels of greenhouse gases.